1. Field of the Invention controlling displaceable pressure rollers during the start-up of coiling of strips in reeling installations, wherein the pressure rollers are displaceable by means of pressure medium-operated cylinders. The beginning of the strip of the entering strip is detected and followed during the travel of the strip around the mandrel and the position of the strip beginning is utilized for positioning the pressure rollers. Before the strip beginning enters and before the next coil is placed, the pressure rollers are raised to such an extent that the gap formed between pressure roller and mandrel exceeds the thickness of the strip which has already entered by a dimension which exceeds the strip thickness. After passing of the strip beginning, the pressure roller is again lowered from this position against the mandrel into the position of operation of the pressure roller.
2. Description of the Related Art
A control installation of the above-described type is known from, for example, German patent 33 18 031. In that installation, during coiling of strips onto reels, the strip beginning is pressed against the reel by means of rollers. In order to keep damage to the strip and the pressure rollers as small as possible, and before passing of a step formed by the strip beginning, the pressure rollers are spaced apart by a dimension which is greater than n times the strip thickness, wherein n is the number of layers of the strip already placed on the mandrel in the region of the respective pressure roller. After the step formed by the strip beginning has passed, the respective pressure roller is switched to pressure. This type of control method has become known as a step control.
It has been found that the step control method leads to satisfactory coiling results when strips are coiled which have a thickness which is greater than approximately 6 mm. However, the step control method is not acceptable for coiling thin strips. The pressure rollers when switched to pressure press the thin strip into the indentations formed between the segments of the reel when the mandrel is spread apart, so that the strip receives undesirable markings. As a result, large portions of the strip beginnings become scrap. In addition, a high load acts on the pressure rollers when they are lowered into the indentations between the individual segments, so that substantial wear of the pressure rollers occurs and significant noise is generated. Moreover, the unsteady positions of the pressure rollers on the reel cause the adjusting devices for the pressure rollers to be worn excessively.